Nonwoven fabrics are useful for a wide variety of applications, such as in wipers, towels, industrial garments, medical garments, medical drapes, sterile wraps, etc. It is not always possible, however, to produce a nonwoven fabric having all desired attributes for a given application. As a result, it is often necessary to treat nonwoven fabrics by various means to impart desired properties. For example, in some applications, barrier properties to organic solvents and oil penetration are desired.
Fabrics that can repel organic solvents can be achieved by fluorination of the material surface(s). Such fluorination has traditionally been performed by those skilled in the art via surface coating techniques of fluoropolymers having at least 8 perfluorinated carbons, and more recently, via surface grafting of fluorinated acrylic monomers bearing an end chain having at least 8 perfluorinated carbons. In particular, the conventional wisdom in the art is that liquid repellency or barrier properties to organic solvents reduces significantly with less than 8 perfluorinated carbons due to the shorter perfluorinated carbon chain making the polymer more receptive to organic solvents, as discussed in “Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkyl acrylate) Thin Films”, K. Honda, et al., Macromolecules, 2005, 38, p. 5699-5705. The chain length of the fluorinated acrylic monomer directly impacts its chemical repellency performance, with shorter chain lengths reducing its liquid repellency property.
However, fluorinated acrylic monomers bearing an end chain having at least 8 perfluorinated carbons, and their resulting products and polymers, have significant environmental disadvantages. In particular, these fluorinated acrylic products bearing end chains having at least 8 perfluorinated carbons (“C8”) are associated with perfluorooctanoic acid (PFOA) either as a processing aid residue during manufacturing or as a potential decomposition by-product of a C8 compound.
PFOA is a synthetic chemical that does not occur naturally in the environment, but has become very persistent in the environment and found at very low levels both in the environment and in the blood of the general U.S. population. Additionally, PFOA has been found to remain in people for a very long time and has been shown to cause developmental and other adverse effects in laboratory animals. These disadvantages of PFOA are so profound that the U.S. Environmental Protection Agency (EPA), in cooperation with major companies in the industry, launched the “2010/15 PFOA Stewardship Program,” in which companies committed to reduce global facility emissions and product content of PFOA and related chemicals by 95 percent by 2010, and to work toward eliminating emissions and product content by 2015.
Accordingly, there exists a need for a nonwoven fabric having suitable liquid repellency or barrier properties to organic solvents and oil penetration without the presence of fluorinated acrylic monomers bearing an end chain having at least 8 perfluorinated carbons and without the use of PFOA as a chemical in the manufacturing and without the risk of yielding PFOA by-product.